US4399325A - Demodulating circuit for controlling stereo separation - Google Patents

Demodulating circuit for controlling stereo separation Download PDF

Info

Publication number
US4399325A
US4399325A US06/212,206 US21220680A US4399325A US 4399325 A US4399325 A US 4399325A US 21220680 A US21220680 A US 21220680A US 4399325 A US4399325 A US 4399325A
Authority
US
United States
Prior art keywords
signal
stereo
accordance
separation
electric field
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US06/212,206
Other languages
English (en)
Inventor
Kanji Tanaka
Noboru Usui
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Sanyo Electric Co Ltd
Original Assignee
Tokyo Sanyo Electric Co Ltd
Sanyo Electric Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Tokyo Sanyo Electric Co Ltd, Sanyo Electric Co Ltd filed Critical Tokyo Sanyo Electric Co Ltd
Assigned to TOKYO SANYO ELECTRIC CO., LTD.,, SANYO ELECTRIC CO., LTD., reassignment TOKYO SANYO ELECTRIC CO., LTD., ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: TANAKA KANJI, USUI NOBORU
Application granted granted Critical
Publication of US4399325A publication Critical patent/US4399325A/en
Assigned to SANYO ELECTRIC CO., LTD. reassignment SANYO ELECTRIC CO., LTD. ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: TOKYO SANYO ELECTRIC CO., LTD., A CORP OF JAPAN
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04H—BROADCAST COMMUNICATION
    • H04H40/00—Arrangements specially adapted for receiving broadcast information
    • H04H40/18—Arrangements characterised by circuits or components specially adapted for receiving
    • H04H40/27—Arrangements characterised by circuits or components specially adapted for receiving specially adapted for broadcast systems covered by groups H04H20/53 - H04H20/95
    • H04H40/36—Arrangements characterised by circuits or components specially adapted for receiving specially adapted for broadcast systems covered by groups H04H20/53 - H04H20/95 specially adapted for stereophonic broadcast receiving
    • H04H40/45—Arrangements characterised by circuits or components specially adapted for receiving specially adapted for broadcast systems covered by groups H04H20/53 - H04H20/95 specially adapted for stereophonic broadcast receiving for FM stereophonic broadcast systems receiving
    • H04H40/72—Arrangements characterised by circuits or components specially adapted for receiving specially adapted for broadcast systems covered by groups H04H20/53 - H04H20/95 specially adapted for stereophonic broadcast receiving for FM stereophonic broadcast systems receiving for noise suppression
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/06—Receivers
    • H04B1/16—Circuits
    • H04B1/1646—Circuits adapted for the reception of stereophonic signals
    • H04B1/1661—Reduction of noise by manipulation of the baseband composite stereophonic signal or the decoded left and right channels
    • H04B1/1669—Reduction of noise by manipulation of the baseband composite stereophonic signal or the decoded left and right channels of the demodulated composite stereo signal
    • H04B1/1676—Reduction of noise by manipulation of the baseband composite stereophonic signal or the decoded left and right channels of the demodulated composite stereo signal of the sum or difference signal

Definitions

  • the curve A shows a signal to noise ratio on the occasion of a monaural state and the curve B shows a signal to noise ratio of a stereo state.
  • a signal to noise ratio has a close relation with a stereo separation. More specifically, the smaller the stereo separation the better the signal to noise ratio. Accordingly, by adjusting a stereo separation a signal to noise ratio is improved. Therefore, the above referenced patent is aimed to improve a signal to noise ratio by controlling the same as shown by the curve D in FIG. 1 by controlling the separation as shown as the curve C in FIG. 1.
  • the degree of improvement of a signal to noise ratio with respect to a change of a stereo separation is not necessarily in a proportional relation. Accordingly, a decrease in a stereo separation does not necessarily achieve an improvement in a signal to noise ratio. For example, even if the stereo separation is decreased from 50 dB to 40 dB, the improvement in a signal to noise ratio is approximately 0.2 dB at the most. Even if a separation is changed from 40 dB to 30 dB, the improvement in a signal to noise ratio is approximately 0.3 dB.
  • the present invention is adapted to maintain stereo separation undecreased until an electric field strength decreases to a predetermined value, to abruptly decrease stereo separation when an electric field strength becomes smaller than the above described predetermined value, and to change separation in accordance with an electric field strength in the range smaller than the above described predetermined value, whereby a discontinuous change of separation is imparted between the stereo state and the monaural state.
  • the above described predetermined value of the electric field strength is selected to be a value which is sufficiently effective in improving a signal to noise ratio by changing stereo separation. According to the present invention, the other problem which is encountered with the previously referenced prior art is totally solved. Therefore, according to the present invention, a stereo receiver of a better signal to noise ratio is provided without degrading stereo separation as a whole.
  • a signal representing a level of an electric field strength is threshold detected, so that a control signal for abruptly decreasing the magnitude of the electric field strength when the same becomes smaller than a predetermined electric field strength and stereo separation is controlled in accordance with the magnitude of the above described control signal.
  • a stereo receiver of a better signal to noise ratio is implemented with a more simplified circuit configuration without degrading stereo separation as a whole.
  • a principal object of the present invention is to provide a demodulating circuit in a stereo receiver, wherein a discontinuous change in separation is attained between the stereo state and the monaural state in accordance with an electric field strength, whereby a better signal to noise ratio is attained without degrading the degree of separation as a whole.
  • FIG. 1 is a graph showing a change of stereo separation and a signal to noise ratio with respect to an electric field strength in accordance with a prior art apparatus of interest to the present invention
  • FIGS. 7, 8A and 8B and 9 are graphs for explaining the operation of the above described embodiment
  • FIG. 10 is a schematic diagram of a major portion for explaining another embodiment of the present invention.
  • FIGS. 11 to 13 are schematic diagrams showing major portions of different embodiments of a signal converting circuit.
  • FIG. 3 is a graph for explaining the principle of the present invention, in which a change of separation and a signal to noise ratio with respect to an electric field strength for reception.
  • stereo separation is maintained approximately a constant value irrespective of the electric field strength within the range IV of the electric field strength (corresponding to II+III of the previously described FIG. 1 graph).
  • the above described constant value may be a possible maximum value inherent to a stereo receiver. If and when the electric field strength becomes smaller than a given predetermined value, i.e. at the boundary between the ranges IV and V, the stereo separation is abruptly decreased to a given value.
  • the above described given value lies between a stereo state and a monaural state as a matter of course.
  • the separation is changed in accordance with the electric field strength. More specifically, in the range V the stereo separation is made larger when the electric field strength is larger, while the stereo separation is made smaller when the electric field strength is smaller. Therefore, according to the present invention, a discontinuous separation change is achieved with respect to a change of the electric field strength, as shown by the curve E shown in FIG. 3.
  • FIG. 4 is a block diagram showing a preferred embodiment of the present invention.
  • the embodiment shown in FIG. 4 comprises an FM stereo receiver.
  • An electric wave as frequency modulated is received by an antenna 1.
  • a high frequency signal received by the antenna I is amplified by a high frequency amplifier 3 and the output therefrom is applied to a mixer 5.
  • the mixer 5 mixes the received high frequency signal with a local oscillation signal obtained from a local oscillator 7, thereby to provide an intermediate frequency signal.
  • the intermediate frequency signal is amplified by an intermediate frequency amplifier 9 and is applied to an FM detector 11 such as a quadrature detector.
  • the FM detector 11 detects the intermediate frequency signal, thereby to provide a low-frequency stereo composite signal.
  • the stereo composite signal obtained from the FM detector is applied to a stereo decoder 13.
  • an intermediate frequency signal as not amplitude limited by a limiter is applied from the intermediate frequency amplifier 5 to a signal converter 15.
  • a voltage signal V IF has the magnitude associated with the level of the intermediate frequency signal, i.e. the level of the electric field strength for reception.
  • the signal converter 15 receives the voltage signal V IF , thereby to provide a control signal voltage V CNT .
  • the control voltage signal V CNT is applied to a switching signal supply circuit 17.
  • the switching signal supply circuit 17 is further supplied with a 38 kHz signal, i.e. a subcarrier signal, obtained from a 38 kHz signal generator 19.
  • FM stereo composite signals include L&R channel information, L-R channel information suppressed carrier modulated on 38 kHz and a19 kHz pilot signal locked to the 38 kHz subcarrier at the transmitter.
  • the 38 kHz signal generator 19 comprises a phase locked loop. More specifically, the stereo composite signal obtained from the FM detector 11 is applied to one input of a phase comparator 191. The other input of the phase comparator 191 is connected to receive a signal obtained from a frequency divider 196 and the output of the phase comparator 191 provides a pulse having the pulse width associated with a phase difference of the two applied signals.
  • the phase difference pulse is integrated by a low-pass filter 192 and the output therefrom is amplified by a direct current amplifier 193 and is applied to a voltage controlled oscillator 194 as a control voltage.
  • the voltage controlled oscillator 194 makes oscillation at the frequency of 76 kHz.
  • the 76 kHz signal obtained from the voltage controlled oscillator 194 is applied to the frequency divider 195, so that the frequency is divided at the frequency division ratio of 1/2. Accordingly, the output of the frequency divider 195 becomes a 38 kHz signal, i.e. a subcarrier signal.
  • the output from the frequency divider 195 is applied to the previously described frequency divider 196.
  • FIG. 6 is a schematic diagram showing in detail a preferred embodiment of the present invention. Referring to FIG. 6, only the signal converter 15, the switching signal supply circuit 17 and the stereo decoder 13 shown in FIG. 4 are illustrated in detail.
  • the stereo decoder 13 of the embodiment shown is of a switching type and is adapted to receive a stereo composite signal obtained from the FM detector 11 (FIG. 4).
  • the stereo decoder 13 comprises a first differential switching stage 134 including transistors 135 and 136, and a second differential switching stage 137 including transistors 138 and 139.
  • the above described stereo composite signal is received by a differential amplifying stage 131 including transistors 132 and 133.
  • the differential amplifying stage 131 provides the stereo composite signal to the above described first and second differential switching stages 134 and 137.
  • a resistor 152 is connected between the emitter and base electrodes of the transistor 151 and the base electrode of the transistor is connected to the ground through a resistor 153.
  • the circuit 15 provides a control voltage signal V CNT representing a discontinuous change as shown in FIG. 7 as a function of the voltage signal V IF as applied. More specifically, in the case where the voltage signal V IF is smaller than a predetermined value, the transistor 151 is non-conductive and accordingly a voltage signal V IF as voltage divided by the resistors 155 and 154 is obtained as a control voltage signal V CNT . If and when the voltage signal V IF becomes larger than a predetermined value, the transistor 151 turns to a conductive state.
  • the resistor 155 connected between the emitter and collector electrodes of the transistor 151 is short-circuited by the transistor 151. Accordingly, the voltage signal V IF as voltage divided by the internal resistance of the transistor 151 and the resistor 154 is obtained as a control voltage signal V CNT .
  • the internal resistance of the transistor 151 is quite small and accordingly the control voltage signal V CNT rapidly increases as shown in FIG. 7. Thereafter the voltage V CNT increases in accordance with an increase of the voltage V IF .
  • the control voltage signal V CNT represents an abrupt, i.e. a discontinuous change.
  • the voltage signal V CNT representing the above described discontinuous change obtained from the signal converter 15 is applied to the base electrode of a controlling transistor 171 of the switching signal supply circuit 17.
  • the emitter electrode of the control transistor 171 is connected to the base electrode of the constant current transistor 172 through a resistor and the base electrode of the transistor 172 is further connected to the ground through a diode 173.
  • the constant current transistor 172 is aimed to determine an operating current of the transistors 175 and 176.
  • the transistors 175 and 176 constitute the switching signal supply stage 174.
  • the base electrodes of the transistors 175 and 176 are supplied with a subcarrier signal, i.e. a 38 kHz signal obtained from the 38 kHz signal generator 19 (FIGS. 4 and 5).
  • the switching signal supply stage 174 controls the level of the 38 kHz signal, i.e. the subcarrier signal as a function of the magnitude of the control voltage signal V CNT being applied and the subcarrier signal the level of which is controlled is applied to the above described stereo decoder as a switching signal. Meanwhile, when the level of the subscriber signal is changed, the demodulation efficiency of the stereo decoder 13 is changed in accordance therewith and accordingly a change of stereo separation is caused. Therefore, the circuits 15 and 17 cooperates with each other to control the demodulation efficiency by the stereo decoder 13.
  • FIGS. 8a, 8b and 9 the FIG. 6 embodiment will be described in detail.
  • the electric field strength of the signal received by the antenna 1 (FIG. 4) is sufficiently small.
  • the voltage signal V IF obtained from the intermediate frequency amplifier 9 is quite small and accordingly the control voltage signal V CNT is also small. Therefore, the control transistor 171 and the constant current transistor 172 included in the switching signal supply circuit 17 both become non-conductive. Accordingly, the transistors 175 and 176 of the switching signal supply stage 174 both become non-conductive and hence the stereo decoder 13 is not supplied with a 38 kHz signal. Accordingly, the respective transistor constituting the first and second differential switching stages 134 and 137 become a fully conductive state. Therefore, the stereo composite signal being applied is not subjected to any switching control and accordingly the same is withdrawn as the left channel signal and the right channel signal of the stereo decoder 13. In such a state a complete monaural state is achieved.
  • the voltage signal V IF supplied from the intermediate frequency amplifier 9 to the signal converter 15 also has a certain magnitude and accordingly the voltage signal V IF is obtained as a voltage signal V CNT voltage divided by means of the resistors 155 and 154. Therefore, in the case where the electric field strength is smaller than a predetermined value, the control voltage signal V CNT changes at a relatively low level as a function of the electric field strength. Accordingly, the level of the switching signal obtained from the switching signal supply circuit 17 also changes depending on the magnitude of the control voltage signal V CNT .
  • the control voltage signal V CNT obtained from the signal converter 15 rapidly increases responsive to conduction of the transistor 151 at the G point (FIG. 8A). Therefore, the base voltage of the control transistor 171 included in the switching signal supply circuit 171 also abruptly increases to become approximately equal to the voltage signal V IF . Thereafter the control voltage signal V CNT also increases in accordance with the increase of the voltage signal V IF obtained from the intermediate frequency amplifier 9. On the other hand, when the base voltage of the control transistor 171 increases, the collector current of the constant current transistor 172 also increases. Accordingly, the level of the subcarrier, i.e.
  • the 38 kHz switching signal, supplied from the switching signal supply stage 174 to the stereo decoder 13 also decreases. Therefore, the 38 kHz switching signal and the stereo composite signal obtained through the differential amplifying stage 131 are subjected to a multiplying operation at the first and second differential switching stages 134 and 137 of the stereo decoder 13. This means that the stereo composite signal is switched in such a state where complete stereo separation is not attained. As the magnitude of the control voltage signal V CNT increases, the operation enters into a more complete stereo state. When the level of the 38 kHz switching signal applied to the stereo decoder 13 reaches a predetermined value as large as 100 mVp-p, for example, thereafter the first and second differential switching stages 134 and 137 perform a complete switching operation. Therefore, in such a state stereo separation by the stereo decoder 13 becomes a possible maximum value inherent to the decoder 13.
  • the FIG. 11 embodiment employs a relay 156 and a relay contact 156a in place of the transistor 151 in the FIG. 6 embodiment.
  • the relay 156 is kept deenergized and the contact 161a is kept off. Accordingly, the output or the control voltage signal V CNT is obtained by dividing the voltage signal V CNT by means of the resistors 155 and 154.
  • the relay 156 is energized and the contact 156a is turned on. Accordingly, as in the case of the previously described embodiment, the resistor 155 is short-circuited at that time and the control voltage V CNT abruptly increases to become substantially the same level as that of the voltage signal V IF .
  • the FIG. 12 embodiment employs a level detector 159 of such as a Schmitt trigger circuit for the purpose of controlling the transistor 151 to be conductive or non-conductive. More specifically, the input of the level detector is supplied with the voltage signal V IF from the intermediate frequency amplifier 9 as voltage divided by means of the resistors 157 and 158. If and when the voltage at the junction of the series connection of the resistors 157 and 158 exceeds a predetermined threshold value, a voltage is obtained from the Schmitt trigger circuit, i.e. the level detector 157. Therefore, the transistor 151 is rendered conductive. Accordingly, even in the case of the FIG. 12 embodiment, when the voltage V IF reaches a predetermined value, the control voltage V CNT abruptly increases.
  • a level detector 159 of such as a Schmitt trigger circuit for the purpose of controlling the transistor 151 to be conductive or non-conductive. More specifically, the input of the level detector is supplied with the voltage signal V IF from the intermediate frequency amplifier 9 as voltage divided by means of the resistor
  • the FIG. 13 embodiment employs a switching element 151' of such as a silicon controlled rectifier in place of the transistor 151 of the previously described FIG. 12 embodiment.
  • the FIG. 13 embodiment is substantially the same as the FIG. 12 embodiment, except for the above described respect.
  • the above described embodiments utilized the intermediate frequency signal as not limited obtained from the intermediate frequency amplifier 9, i.e. the voltage signal V IF , for the purpose of generating a signal having the magnitude associated with the level of the electric field strength of a signal being received.
  • a signal proportional to the level of the electric field strength may be a voltage signal obtained by detecting the level of the so called white noise and inverting the same, and may be obtained by utilizing other various well-known circuits.
  • the previously described embodiments have been adapted to control the stereo separation so that the signal to noise ratio may be approximately constant in the range V of the electric field strength.
  • a change of the stereo separation in the range V i.e.
  • a manner of the change of the signal to noise ratio may be arbitrarily selected by a mere designing change.
  • the present invention is adapted such that the stereo separation is abruptly degraded when the electric field strength becomes smaller than a predetermined value, so that a discontinuous change of the stereo separation is attained.

Landscapes

  • Engineering & Computer Science (AREA)
  • Signal Processing (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Stereo-Broadcasting Methods (AREA)
US06/212,206 1979-12-28 1980-12-02 Demodulating circuit for controlling stereo separation Expired - Lifetime US4399325A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP54-172100 1979-12-28
JP54172100A JPS5854692B2 (ja) 1979-12-28 1979-12-28 ステレオマルチプレックス回路

Publications (1)

Publication Number Publication Date
US4399325A true US4399325A (en) 1983-08-16

Family

ID=15935536

Family Applications (1)

Application Number Title Priority Date Filing Date
US06/212,206 Expired - Lifetime US4399325A (en) 1979-12-28 1980-12-02 Demodulating circuit for controlling stereo separation

Country Status (3)

Country Link
US (1) US4399325A (fr)
JP (1) JPS5854692B2 (fr)
DE (1) DE3048409A1 (fr)

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3521099A1 (de) * 1985-06-14 1986-12-18 Pioneer Electronic Corp., Tokio/Tokyo Stereophone empfangsschaltung
US4646348A (en) * 1985-07-18 1987-02-24 National Semiconductor Corporation Blend control for low voltage stereo decoders
US4703501A (en) * 1985-05-17 1987-10-27 Pioneer Electronic Corporation Sound multiplex receiver
DE4235909A1 (de) * 1992-10-23 1994-04-28 Telefunken Microelectron Mono/Stereo-Umschalter
EP2073409A1 (fr) * 2007-12-21 2009-06-24 Fujitsu Ten Limited Procédé de suivi de réseau et appareil de radio pour utilisation embarquée
US20090232316A1 (en) * 2008-03-14 2009-09-17 Chieh-Hung Chen Multi-channel blend system for calibrating separation ratio between channel output signals and method thereof
US20090252337A1 (en) * 2008-04-08 2009-10-08 Chieh-Hung Chen Multi-channel decoding systems capable of reducing noise and methods thereof
US20090310791A1 (en) * 2008-06-17 2009-12-17 Tien-Ju Tsai Method for processing an input composite signal and signal processing apparatus thereof
USRE42949E1 (en) * 1992-09-21 2011-11-22 Hybrid Audio Llc Stereophonic audio signal decompression switching to monaural audio signal

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2001140731A (ja) 1999-11-15 2001-05-22 Bosch Automotive Systems Corp 電磁式燃料噴射弁

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3573382A (en) * 1969-02-06 1971-04-06 Motorola Inc A stereophonic receiver muting means with substitution of a dc circuit for an ac circuit
US3617641A (en) * 1969-02-07 1971-11-02 Motorola Inc Stereo multiplex demodulator
US3673342A (en) * 1969-08-02 1972-06-27 Braun Ag Circuit arrangement for improving the signal-to-noise ratio of a stereo decoder
US3707603A (en) * 1969-12-29 1972-12-26 Rca Corp Fm stereophonic receiver detection apparatus and disabling means
US3790714A (en) * 1970-07-13 1974-02-05 Sony Corp Fm stereophonic receiver
US4049918A (en) * 1975-10-09 1977-09-20 Sony Corporation MPX stereo signal demodulator
US4251690A (en) * 1978-07-28 1981-02-17 Toko, Inc. Frequency-modulation stereophonic receiver

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3573382A (en) * 1969-02-06 1971-04-06 Motorola Inc A stereophonic receiver muting means with substitution of a dc circuit for an ac circuit
US3617641A (en) * 1969-02-07 1971-11-02 Motorola Inc Stereo multiplex demodulator
US3673342A (en) * 1969-08-02 1972-06-27 Braun Ag Circuit arrangement for improving the signal-to-noise ratio of a stereo decoder
US3707603A (en) * 1969-12-29 1972-12-26 Rca Corp Fm stereophonic receiver detection apparatus and disabling means
US3790714A (en) * 1970-07-13 1974-02-05 Sony Corp Fm stereophonic receiver
US4049918A (en) * 1975-10-09 1977-09-20 Sony Corporation MPX stereo signal demodulator
US4251690A (en) * 1978-07-28 1981-02-17 Toko, Inc. Frequency-modulation stereophonic receiver

Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4703501A (en) * 1985-05-17 1987-10-27 Pioneer Electronic Corporation Sound multiplex receiver
DE3521099A1 (de) * 1985-06-14 1986-12-18 Pioneer Electronic Corp., Tokio/Tokyo Stereophone empfangsschaltung
US4646348A (en) * 1985-07-18 1987-02-24 National Semiconductor Corporation Blend control for low voltage stereo decoders
USRE42949E1 (en) * 1992-09-21 2011-11-22 Hybrid Audio Llc Stereophonic audio signal decompression switching to monaural audio signal
DE4235909A1 (de) * 1992-10-23 1994-04-28 Telefunken Microelectron Mono/Stereo-Umschalter
DE4235909C2 (de) * 1992-10-23 2003-01-02 Atmel Germany Gmbh Mono/Stereo-Umschalter
EP2073409A1 (fr) * 2007-12-21 2009-06-24 Fujitsu Ten Limited Procédé de suivi de réseau et appareil de radio pour utilisation embarquée
US20090232316A1 (en) * 2008-03-14 2009-09-17 Chieh-Hung Chen Multi-channel blend system for calibrating separation ratio between channel output signals and method thereof
US20090252337A1 (en) * 2008-04-08 2009-10-08 Chieh-Hung Chen Multi-channel decoding systems capable of reducing noise and methods thereof
US8094836B2 (en) 2008-04-08 2012-01-10 Mediatek Inc. Multi-channel decoding systems capable of reducing noise and methods thereof
US8559653B2 (en) 2008-04-08 2013-10-15 Mediatek Inc. Multi-channel decoding systems capable of reducing noise and methods thereof
US20090310791A1 (en) * 2008-06-17 2009-12-17 Tien-Ju Tsai Method for processing an input composite signal and signal processing apparatus thereof
US8964991B2 (en) * 2008-06-17 2015-02-24 Himax Tehnologies Limted Method for processing an input composite signal and signal processing apparatus thereof

Also Published As

Publication number Publication date
DE3048409A1 (de) 1981-09-17
JPS5694856A (en) 1981-07-31
DE3048409C2 (fr) 1987-10-01
JPS5854692B2 (ja) 1983-12-06

Similar Documents

Publication Publication Date Title
US4380824A (en) Receiving reproducing system
US3573382A (en) A stereophonic receiver muting means with substitution of a dc circuit for an ac circuit
EP0030874B1 (fr) Circuit de réduction des distorsions pour un récepteur à modulation de fréquence
US4356350A (en) FM Receiver
US4399325A (en) Demodulating circuit for controlling stereo separation
US4063039A (en) Stereo noise reduction circuit
US3825697A (en) Phase-lock-loop fm-stereo decoder including stereophonic/monophonic blend system for reducing audio distortion
US4146747A (en) Fm stereo demodulating device
US4047116A (en) FM multiplex stereo demodulating circuit
US4368355A (en) AM Stereophonic signal receiver with electric field strength detection
US4466115A (en) FM Stereo signal demodulator
US4449230A (en) Apparatus for demodulating an AM stereophonic signal
US4289981A (en) Pulsive component detecting apparatus
JPS6217907B2 (fr)
EP0047522B1 (fr) Circuit pour identification d'un signal stéréophonique
US4710958A (en) Circuit for controlling separation and high-cut operation of a stereo demodulator in an FM radio receiver
US4251690A (en) Frequency-modulation stereophonic receiver
JPS5853531B2 (ja) ステレオ復調回路
JPS6223501B2 (fr)
JP2723187B2 (ja) 音声多重復調回路
JPS6314516Y2 (fr)
JPS632181B2 (fr)
JPS6221460B2 (fr)
JPS5853533B2 (ja) ステレオ復調回路
GB2040145A (en) Improvements in F.M. receivers

Legal Events

Date Code Title Description
STCF Information on status: patent grant

Free format text: PATENTED CASE

AS Assignment

Owner name: SANYO ELECTRIC CO., LTD., 18, KEIHANHONDORI 2-CHOM

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:TOKYO SANYO ELECTRIC CO., LTD., A CORP OF JAPAN;REEL/FRAME:004642/0964

Effective date: 19861106

Owner name: SANYO ELECTRIC CO., LTD., JAPAN

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:TOKYO SANYO ELECTRIC CO., LTD., A CORP OF JAPAN;REEL/FRAME:004642/0964

Effective date: 19861106